Compared to her younger sister, Mamiko sports lighter brown hair and burgundy eyes, but they both have wavy hair, though Mamiko's is less wavy and is longer. She has brown-reddish eyes, which is inherited from her father. She is usually seen with makeup and is often dressed in a baggy sweater-like top and a brown skirt.
Mamiko barges in Kumiko's room on occasion to check up on the latter, much to the younger sister's chagrin.
At a young age, Mamiko has been an experienced trombone player, and she was the one responsible for both Kumiko and Shuuichi's interest in playing brass instruments.
Mamiko finds out that Kumiko has not only changed her hairstyle into a ponytail but that she's considering giving up on playing brass instruments for good. She visits her younger sister to hear about her sentiments about the issue, but was quickly shooed away when she caught Kumiko talking to her cactus plant alone. Mamiko's comment on Kumiko's hair made the latter reconsider about changing her look at school and Kumiko eventually decides to wear her hair loose like in her middle school days.
In the Episode 4 Season 2, she runs into a quarrel with her parents, which is later revealed due to her wanting to pursue her goal to attend a beauty school against her parents wishes.